Various lens-fitted photo film units preloaded with photo films are on the market. Among such lens-fitted photo film units, those which improve their imaging characteristics by enabling selecting photography modes according to brightness are known. For example “Night & Day” (a trade name) is produced and sold by the present applicant.
The above-mentioned lens-fitted photo film unit is loaded with a high-speed photo film, and is provided with three photography modes: a day-light photography mode (with no flash light) and a day-light synch-flash photography mode (with flash light) to deal with photographing in such a bright place as outdoors in the daytime and a night-view synch-flash photography mode to deal with photographing such a dark subject as a night view or photographing with flash light a main subject like people with a dark background like a night view or a dark inside of a room while reproducing the background at an appropriate density.
To be more precise, a film speed of the photo film is ISO1600. The day-light and day-light synch-flash photography modes set a shutter speed at 1/120 seconds and an aperture size at f/14 in f-number. The night-view synch-flash photography mode sets the shutter speed at 1/45 seconds and the aperture size at f/6.2. According to this, as an exposure value (EV) is based on ISO100, an appropriate exposure value is EV10.8 in the day-light and day-light synch-flash photography modes and EV7.0 in the night synch-flash photography mode.
Using the above-mentioned high-speed photo film allows widening the range of brightness the night-view synch-flash photography mode can deal with while maintaining the usefulness. However in the event that the appropriate exposure value is switched by two stages as described above, it is impossible to fully exploit advantages of using the high-speed photo film. For example, it becomes possible to photograph quite dark scenes by lowering the shutter speed so far as it would not induce shaking and making the aperture size as large as possible for the night-view synch-flash photography mode.
In that case, however, such a brightness range that is beyond capacity of the camera would turn up between a brightness range covered by the night-view synch-flash photography mode and one covered by the day-light and day-light synch-flash photography modes set for photographing outdoors in the daytime. For example a preferable imaging characteristics cannot be gained in a dim inside of a room even in any photography modes. On the contrary, setting the proper exposure value for the night-view synch-flash photography mode closer to one for the day-light and day-light synch-flash photography modes makes it impossible to photograph a darker scene that is to be dealt with by the night-view synch-flash mode while maintaining the usefulness.